Thursday, December 3, 2009

Probable Pair-Instability Supernovae Explosion

Scientists seem to have observed the explosion last year of a 200 solar-mass star. Stars this big are rare today but are thought to have been common in the early universe. The heavy elements forged together in that massive nuclear furnace were detected in surprising amounts, leading scientists to regard Supernovae SN 2007bi as relevant to the early evolution of the universe.

"The heavy elements spewed into space in the deaths of similar early, massive stars may have stunted the growth of later stellar generations. That's because gas clouds containing iron and other heavy elements tend to fragment into smaller knots that give birth to relatively lightweight stars like the sun....

Though some less-massive stars also spew metals when they die, pair-instability supernovae are especially prolific polluters. "One such explosion can pollute an entire small ancient galaxy," Gal-Yam told New Scientist... The dwarf galaxy where SN 2007bi occurred seems to have low metal content, the team says, which might explain how the star that went supernova was able to form."

Stars born with more than about 140 times the mass of the sun die as "pair-instability supernova" that spew heavy elements into space (Illustration: NASA/CXC/M Weiss)